Here are the St John NPS rules regarding trash disposal:

66. Trash being disposed from vessels may not exceed two 10-gallon bags and must fit inside NPS trash containers identified for vessel trash in Francis Bay, Leinster Bay, Salt Pond, Great Lameshur Dock, and Little Lameshur Bay.

Here's the link to the NPS regs: https://www.nps.gov/viis/learn/management/index.htm